Engineering cryogenic setups for 100-qubit scale superconducting circuit systems

Abstract

A robust cryogenic infrastructure in form of a wired, thermally optimized dilution refrigerator (DR) is essential for present and future solid-state based quantum processors. Here, we engineer an extensible cryogenic setup, which minimizes passive and active heat loads, while guaranteeing rapid qubit control and readout. We review design criteria for qubit drive lines, flux lines, and output lines used in typical experiments with superconducting circuits and describe each type of line in detail. The passive heat load of stainless steel and NbTi coaxial cables and the active load due to signal dissipation are measured, validating our robust and extensible concept for thermal anchoring of attenuators, cables, and other microwave components. Our results are important for managing the heat budget of future large-scale quantum computers based on superconducting circuits.

Controlling phonons and photons at the wavelength scale: integrated photonics meets integrated phononics

“…To suppress decoherence, these microwave circuits are operated at millikelvin temperatures inside dilution refrigerators. Heat generation must be restricted in these cold environments [233]. The most advanced prototypes currently consist of on the order of fifty qubits on which gates with at best 0.1% error rates can be applied [233,234].…”

“…Heat generation must be restricted in these cold environments [233]. The most advanced prototypes currently consist of on the order of fifty qubits on which gates with at best 0.1% error rates can be applied [233,234]. Scaling up these systems to millions of qubits, as required for a fully error-corrected quantum computer, is a formidable unresolved challenge [229].…”

“…Electro-optic polymers [240] may yield higher interaction rates g 0 but bring along challenges in optical and microwave losses κ and γ µ . Cooling powers of roughly 10 µW at the low temperature stage of current dilution refrigerators [233] imply that conversion rates with common electro-optic materials will likely not exceed about 10 kqbits/s. Considering that the g 0 /κ demonstrated optomechanical devices is much larger than those found in electro-optic systems, and following a reasoning similar to that presented in section 5B for classical modulators, it is likely that microwave-to-optical photon converters based on mechanical elements as intermediaries will be able to achieve large efficiencies.…”

A quantum engineer's guide to superconducting qubits

“…In the case of photon shot-noise, in addition to applying dynamical decoupling techniques, there have been several recent works aimed at reducing the thermal photon flux that reaches the device. This include optimizing the attenuation of the cryogenic setup 106,148,172 , remaking the cryogenic attenuators with more efficient heat sinking 147 , adding absorptive "black" material to absorb stray thermal photons 173,174 , and adding additional cavity filters for thermalization 175 .…”

Resonance inversion in a superconducting cavity coupled to artificial atoms and a microwave background

“…In the following, we call this type of coupling a microwave background. In state-of-the-art superconducting quantuminformation devices [10][11][12][13] a large number of qubits with their control lines are integrated into a small-sized chip, with possible further size-optimization to reduce decoherence mechanisms, such as non-equilibrium quasiparticle tunneling [14] or field focusing [15]. A quantumstate measurement in such circuits is commonly based on microwave transmission through readout resonators [16].…”